The long-term objective of this study is to reduce risk for HIV and other sexually transmitted diseases (STDs) during and after pregnancy among adolescents and young women (aged 14-19) receiving prenatal care in 14 Community Health Centers (CHCs) serving predominantly Black and Latina communities in the New York City Metropolitan area. We will evaluate an innovative model of group prenatal care that integrates HIV prevention (CenteringPregnancy Plus, CP+) and has already yielded favorable biological and behavioral outcomes in a large NIMH-sponsored randomized controlled efficacy trial. Specific aims are to: (1) Translate an efficacious HIV prevention intervention to 14 CHCs;(2) Test the effectiveness of this intervention by (a) examining behavioral and biological outcomes via prospective measurement throughout the prenatal period and up to one year postpartum (N=1400), and (b) identifying potential mechanisms of the effects of group prenatal care, using Bronfenbrenner's Ecological Systems Theory as a guiding framework;and (3) Conduct a rigorous process evaluation to identify factors that influence the uptake, fidelity, and sustainability of this intervention. Using a clustered randomized controlled design, CHCs will be randomly assigned to group care or individual standard of care. We hypothesize that CP+ will be effectively translated to CHCs, and that it will result in significant reductions in HIV-related risk behaviors, significantly lower rates of STDs and repeat pregnancies, as well as improvements in perinatal outcomes. While extensive resources have been devoted to efficacy trials, fewer resources have been devoted to identify the effectiveness of programs implemented in "real world" settings, such as CHCs, where one in ten women - including many at highest risk for HIV/STDs -- receive prenatal care. The proposed research is responsive to the PA-01-123, seeking to support multi-site collaborative intervention trials. This represents an important advance in interdisciplinary HIV prevention research for adolescent women: integrating a theoretically-driven and empirically-validated program for HIV/STD prevention into prenatal care is a promising way to provide sustainable care and disease prevention in a culturally-tailored setting. These underserved patients and the clinicians who care for them represent the ideal beneficiaries of translating clinical research into clinical practice for the reduction of risk and transmission of HIV and other STDs, as well as the elimination of health disparities.